Impact of nanoplastics emitted from incineration of polyethylene plastic on THP-1 macrophage viability and immune function

Inhalation exposure to micro-nanoplastics (MNPs) generated by plastic waste incineration is an emerging public health concern. This study assessed the impact of nanoparticles emitted during the incineration of high-density polyethylene (HDPE-I) on THP-1 lung macrophages. HDPE-I nanoparticles (<0.1 µm) were generated using an Integrated Exposure Generation System and collected with a Compact Cascade Impactor. Elemental and chemical analysis of HDPE-I revealed large amounts of sulfur, multiple metals (aluminum, magnesium, calcium, potassium, and iron), and high concentrations of toxic high molecular weight polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs), including the highly carcinogenic PAH benzo[c]fluorene. The overall carcinogenicity potential of HDPE-I PAHs, in benzo[a]pyrene equivalents (BaP), was 798.02 ng/m, orders of magnitude higher than that of other ambient anthropogenic nanoparticles. Exposure of THP-1 macrophages to HDPE-I increased cytotoxicity and reduced mitochondrial membrane potential, while also impairing phagocytosis by ∼79 %. RNA-seq analysis revealed activation of xenobiotic metabolism and stress-response pathways, particularly through AhR signaling, and altered expression of immune-related genes. These findings suggest that inhalation of MNPs emitted from plastic incineration may compromise alveolar macrophage function, increasing susceptibility to environmental particles and respiratory pathogens. Stricter waste management practices and regulatory policies are required to mitigate plastic burning emissions.